It is so exciting to compare different cultures and languages.
English people use the phrase “Say hello to my close friend”, when they want to greet a person, haven’t seen for a long time.
Russian people use the phrase, that can be better translated as “Send hello to my close friend”, in Russian language it sounds like: “Передавай привет моему другу” 👋
So, Russians think, that they send “hello” as if it were something material 🎁
Compare: “передать подарок” (send a present) and “передать привет” (send hello).
The tradition to consider “привет” (hello) a material thing possibly began a long time ago during The Great Patriotic War when 📬 postal communication was the only way of greeting loved ones in separation. In those days the postman came to the house with an ✉ envelope in his hand and said such phrase: “Вам привет из Ленинграда” 👋 (as far as Saint Petersburg called Leningrad till 1991.)
But today we can tell you: “Вам привет из Санкт Петербурга” 😉